NASA planetary geologist Noah Petro is urging everyone to step outside and soak in the view. At the time of closest approach, the moon will be setting and the sun rising, at least on the U.S. East Coast, so prime viewing will be Sunday and Monday nights there.

"Ultimately, people should be more geared toward just getting outside and enjoying it," Petro said.

Supermoons can appear 14 percent bigger and 30 percent brighter in the night sky. But it takes a real expert to notice the difference.

Petro, deputy project scientist for the Lunar Reconnaissance Orbiter circling the moon, said Thursday that even he won't be able to see much difference in size and luminosity. What counts, he said, is getting people "talking, thinking and caring about the moon."